Auction house Osenat describes it as the first letter written by the French emperor in English on St Helena, after he was defeated in the the Battle of Waterloo and exiled to the British island.
He was determined to learn the language of his British captors, but the letter shows he had not quite the mastery he would have liked, the BBC reported.
The yellowed sheet of paper is one of three written from St Helena by him.
Just after arriving there, Napoleon started daily English lessons given by his aide, Emmanuel, the Comte de las Cases.
Boredom was a spur, as well as a desire to understand what was being communicated around him.
The ex-emperor was a keen student, and soon, when he could not sleep at night, he took to writing short letters to his teacher.
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His prose is not always easy for modern English speakers to understand.
"Count Las Case. It is two o'clock after midnight, I have enow (enough) sleep, I go then finish the night into to cause with you," begins the letter.
"He shall land above seven day, a ship from Europe that we shall give account from anything who this shall have been even to day of first January thousand eight hundred sixteen," it goes on.
The auction will take place in Fontainebleau, south of Paris, on Sunday and is expected to fetch up to USD 100,000.